Method of treating acoustical members and the article produced thereby



Dec. 15, 1931. E. o. SCHWEITZER 1,336,089

METHOD OF TREATING ACOUSTICAL MEMBERS AND THE AH'T CLE PRODUCED THEREBY Filed Sept. 4, 192s f'zverzf'or' Idm and 0. c/zwcz'zzer Patented Dec. 15, 1931 EDMUND 'OVSCHWEITZER, OF CHICAGO, ILLINOIS MOD OF'TBELTING AOOUSTICAL MEIEBERS AND THE ARTICLE PRODUCED THEREBY A pl cation filed fleptember 4, 1928. Serial No. 308,808.

My invention relates to the treatmentof acoustical membersto improve the character of the same. More particularly, it relates to the production of improved (sounding boards for musical instruments.

The tonal qualities of musical instruments employing sounding boards, such forexamfile, as thepiano, the violin, guitar, etc, are argelydependent upon the qualities of the soundin board. The character of the Wood of whic the sounding board is composed is of great "importance. But the intrinsic quality of the wood of the sounding'board, whichinakes one violin sound sweet and melflow and another violin of identical pattern and dimensions sound harsh and noisy, has notheretofore beenunderstood. It has'been enerally represented, by those claiming to f ave knowledge of the facts, that the peculiar varnish employed by the famous Violin makers of Italy is mainly responsible for the sweet tone of the instrument. That is not "wholly correct.

.I have discovered that to make instruvments, .more particularly the sounding "boards thereof, respond in the vproper man- .ner ,to actuating'impulses to fget the desired mellow tones, thermaterial 0' which the instrument or more particularly the sounding board is composed, must be in such condition that it will vibrate in a proper relative manner for each tone of actuationand .be .capabio of responding to such actuating influence to a high degree The sounding board or the bod of the instrument must be responsive in igh-de gree, but such response must be even throughout the range .of playing. To secure the aforesaid condition, the stresses in different parts of the material must be relieved, so that for each tone, the section of material called most actively into play will vibrate properly.

For this purpose, I have found that by treatment of the material to be used for vibratory purposes with ultra violet and similar rays of light, valuable and highly desirable results can vbe attained. The light which I employ has a'lar e percentage of chemically active rays. y observations or structure of the Wood of the-practice of the process and myins ection ofthe treated product lead me to believe that the chemically active rays, decompose and soften the gums and resins contained in the Wood or similar fibrous material and produce an effect in a few days, which is superior to the aging effect of many years, While avoiding the destructive effects of the latter. While I am not able at present to say precisely what change inthe composition and what change in the composition or structure of the varnish takes place there is no doubt as to the improvement in tone which the process of my invention secures. Marked improvement in the acoustic qualities of the wood are obtained withoutany apparent dam e to the strength of the same or injury to t 1e finish or varnish.

The action of the ultra violet rays further effects a tendency of the gums in wood to evaporate and permits the wood to assume a more nearl uniform resilience without destructive e 'ect upon its strength characteristics. To prevent the heating of the material under treatment, air is blown upon the surface while the material is subjected to the action of the ultra violet rays. In the practice ofthis inventoin, I have treated violins by subjecting them to the rays of'a mercury arc lamp having a quartz bulb or tube and remarkableimprovements in the tone qualities have been secured.

I conceive that the same treatment may be employed in improving the tonal qualitiesof sounding boards ofpianos, and bodies of various stringed instruments, such as guitars, mandolins, and the like, and possibly pipe or ans, flutes, and the like.

T do not intend to limit the invention solely to the improvement of wooden members, but intend the same to include such cognate material as will be benefited by treatment with chemically active light rays.

There may be other characteristics of the material which are improved, with which 'I am not, at present, familiar, but I intend that all such features as are secured by the process .and treatment ofmy invention tobe covered thereby, although not now specifically known.

I am not able to say, with scientific accuracy what the change in the character of the wood actually is.

I conceive that the chemically active rays affect the cementitious materials in the wood, both the free gums and resins, which are contained in the pores of the wood and perhaps together.

i the same.

also the gums and resinsor bindin'gmaterials which cement the fibers or cells of the wood Now, in order to acquaint those skilled in the art with the manner of constructing and operating adevicein accordance with my invention, I shall describe, in connection with the accompanying drawings, aspecific embodiment of the same. In the drawings:

Figure 11s a d1agram lllustrating the 'method of treatment of a plate of'wood or the like to improve the qualities of the same for acousticalpurposes; and V Figure 2 is a similar diagram of apparatus j IOI' treating violinsaccording to my invention. 7

5 Referring to Figure 1, I provide a cabinet or container 1, within which I'support'the plate or sheet of wood 2 or other similar material to be treated, as uponthe supports 33.

The upper surface of the wood being exposed to the action of a sourceof ultra violet rays which, in this instance, is shown as a form of V "mercury arc lamp having a quartz bulb so as to permit the passage of the ultra violet rays tor, who may then control the cooling effect of the fan 7, so as to maintain a suitable tempera- "ture. An exit opening. 19, at the top of the casing, permits the current of air which is blown in by the fan 6 .to escape. Z The details of the mercury arc lamp are not "of the essence of this invention and any suitable source of ultra violet light may be eml ployed, for instance, a carbon arc lamp might "besubstituted, although it is to be observed that the'mercury arclamp with a quartz bulb provides a light which is rich in light of extremely high frequency. It is well known that glass is almost completely opaque to ultra violet rays. The usual mercury vapor lamp such as is commonly employed for illu- -minating purposes does not provide any appreciable amount of ultra violet light.

The board or sheet 2 may be finished with a 1 coating of varnish on its surface, as indicated at 10, and apparently the varnish is affected by the treatment, as are the other resins or cementitious constituents of the wood. During treatment, I maintain the temperature of the surface of the wood 2 at approximately 30 Centigrade, and while that temperature alone is not great enough to melt or apparently affect the varnish, the chemical action of the light rays causes the varnish to soften and become tacky and then later show a change in the shade of color, appearing more flexible, and finally it loses its tacky'feeling.

The extent of treatment depends upon the thickness of the wood and its other characteristics for, preferably, the wood is subjected alternately on opposite sides to treatment for a periodlong enoughto produce the desired improvement.

in the case-of treating violins, which I have satisfactorily carried out, as indicated in Figure'2, I had employed a mercury arc lamp with quartz bulb, the specific instrument which I have used being secured on the open market asthe so-called mercury arc lamp universal portable unit, manufactured by the Burdick Corporation, of Milton, Wisconsin. This unit is rated at 110 to 125 volts and normal amperes A. C. 8 and D. C. 4.25, orapproximately 1000 watts input. This quartz, mercury arc lamp I have indicated generally at 11, with a suitable reflector 12 thereabout, to directthe rays intothe cabinet 13 at the bottom of which was disposed the violin 14.

A thermometer, indicated at 15, was laid, upon the body of the instrument, in order to observe the temperature at the surface of the same. The cabinet 13 was two feet by two feet six inches in its horizontal dimensions and about five and one-half feet high. The

violin was placed at the bottom part of the" cabinet in a position so that the vertical distance between the lamp 11 and the topof the violin l lwas approximately three and onehalf feet, the rays from the lamp striking the;

body of the violin as nearly as possible in a verical direction. A cooling blower 16, as indicated in Figure 2, was provided at a pointsuitable to maintain a circulation of air within the cabinet and suitable openings, as at 17,

17, were provided at the top of the'cabin'et 13. In one example, a'violin made by Carl Vogel, of Augsburg, Bavaria, Germany, was exposed to the rays of the Burdick lamp for about six hours per day, alternately one day 7. on thefront side and one day on the back side of the violin, for a total of twenty-four hours.

' At the end of that time, the violin was inspected and tested by actual playing of the instrument and it was found that considerable improvementin tone quality had been obtained. It was further found that the tone quality continued to improve for several days after the treatment had been discontinued. H

In another instance, a new violin bearing the label Leopold Schweicher was exposed to the rays of the mercury arc quartz lamp for approximately six hours per day, alternating the treatment on front and back for a total period of sixty-two hours. This violin, being comparatively new, and not aged in service, showed remarkable improvement in tone quality and continued to show an improvement for several days after the treatment had been discontinued.

The varnish, which was relatively new, showed plainly that it had undergone a change.

These instances show that treating of the wood of the violin with the ultra violet rays causes the wood fiber to undergo some change in fiber structure, perhaps both mechanical and physical and it shows that the aging of the varnish is reatly accelerated by this process, giving the instrument the characteristics and properties such as are found only in old violins played for many years and made of carefully selected wood, possessing the capability of improving in quality wit age and normal use.

The Carl Vogel violin, above referred to, was later given further treatment for twenty-seven hours, a total of fifty-one hours treatment. This additional treatment secured further improvement in tone quality and the improvement progressed further for a few days after the treatment was discontinued, leading to the conclusion that the wood continues to change to a desirable state or condition, due to the action of the chemically active rays.

I am aware that, heretofore, attempts have been made to improve the wood of violins and the like by a heat treatment, having a tendency to affect the resins and gums of the wood, but such a treatment has been found to be effective only temporarily and that in the hands of the user, the so-called heat process which amounts to no more than a high degree of drying out, causes the instrument to deteriorate in tone uality.

The above described treatment with light rays has been applied to a relatively large number of instruments, with uniformly successful results and artists who are competent judges of the tonal qualities have pronounced the instruments treated according to my in} vention as havin amazing superiority over the former condition, that is, before treatment.

I conceive that, in the case of thicker sounding boards, more extensive treatment is necessary than is indicated by the above examples when violins were treated. The exact extent to which such treatment must proceed is, however, within the selection and skill of the operator. Suflice it to say that the treatment definitely benefits the material and provides a means for increasing the value of musical instruments or the constituent parts thereof, and makes it possible to provide new instruments of tone qualities comparable only to those heretofore obtainable in instrumeans long aged in service.

I do not intend to be limited to the precise procedure above outlined, nor to the details of the apparatus disclosed, as the application of the principles of the invention will be apparent to those skilled in the art. The invention may be practiced within wide limits, to secure the beneficial results of which it is capable.

I claim 1. Th process of artificially aging a violin to improve the tone quality thereof. which comprises subjecting the body thereof to the action of ultra violet light so that its tone quality is improved.

2. As an article of manufacture, a sounding board for a stringed musical instrument comprising a thin plate of wood having the surface thereof covered by varnish, the resinous binder of the wood fibers and the varnish on the surface being modified by the incidence of strong chemically active light to render the same responsive substantially uniformly to harmonic vibration throughout a range of musical tones.

3. The method of treating a violin to improve the tone qualities thereof, which comprises subjecting the body thereof to the action of ultra violet light and simultaneously projecting a blast of air upon the surfaces thereof to maintain the varnish at a temperature below the melting point thereof.

4. The method of artificially aging a violin to improve the tone qualities thereof, which comprises intermittently subjecting the same to the action of ultra violet light.

5. The process herein described of improving the character of wood used for the sounding board of a musical instrument and the like which comprises exposing the wood in the form of a thin board to the impingement of strong ultra violet light.

In witness whereof, I hereunto subscribe my name this 29th day of August, 1928.

EDMUND O. SCHWEITZER. 

